It helps if you have long fingers. The PS3 controller I mastered with one hand its nice because it smaller than the PS4 controller. Though not mastered yet, I have become pretty good with the PS4 controller, one handed, the only thing is the touchpad which is very easily "touched" and it activates the cursor. I could change it but what fun would that be.

Battles are not that bad as long as the hotbar is setup with main attacks to one side, defensive to the left (playing as PLD). Macros too will help ( though I don't use them) for short term it may be better. Haven't done any dungeons one handed, but FATES and any other above ground battles aren't bad. Heck I have even used my chin to hit buttons. Gotta do what you gotta do. Though I have been doing this for years, 10 days may not be enough to get the hang of it.